1. Field Of The Invention
This invention relates to an algacide and, in particular relates to an algacide useful in preventing the growth of algae in swimming pools and spas and to prevent and remove yellow algae stains from surfaces of the pools and spas.
2. Brief Statement Of The Prior Art
Many oxidizing agents have been used with limited success to prevent the growth of algae in swimming pools and spas and to prevent the formation of yellow algae deposits on the surfaces of the pools and spas.
Examples of agents which have been used are: chlorine, salts and compounds of metals such as silver and copper, quaternary salts, polyquaternary salts, simazines and others. Unfortunately, the microorganisms, after an exposure period of 1 to 2 years, have adapted to these agents, and algae have been reported growing in waters containing 20 ppm chlorine, which is approximately 10 to 15 times the normal dosage level of chlorine in pool and spa waters.
I have discovered the bromine is a very effective algacide in pools and spas. My early work revealed that bromine was effective at dosages as low as 0.1 ppm. I have now used bromine as an algacide for slightly over two years, and I have found that algae do not adapt to the bromine or acquire a tolerance for this agent.
My use with a bromide algacide, however, has revealed concentration limits to the polyphosphate coadditive. In my initial work, I used mixtures which contained 25 percent of tetra sodium polyphosphate. This mixture caused clouding of the water when used on a regular maintenance program, in which the composition was added as needed to maintain the bromine content in the effective range. In my initial work, the composition was also added at a large excess, however, it was found that this caused depletion of chlorine from the pool water, and the present method of this invention comprises the frequent addition of limited dosages of the composition to the water.